[alsa-devel] Question about Component and Card

[Lars-Peter Clausen]

On 08/03/2015 07:33 AM, Kuninori Morimoto wrote:
> 
> Hi Lars
> Cc Mark
> 
> I noticed my sound card (which is not upstreamed) can't probe in next branch.
> I think it is because this patch
> 1b7c12316982f74a5b8e7704c24cf5524d0723a3
> (ASoC: Prevent components from being bound to multiple cards)
> 
> In my case, my sound device (= CPU) has some DAIs,
> and these are connected to some codecs.
> It is shown as below. And I would like to use these as 2 sound cards.
>  ex)	aplay -D hw:0 xxx
> 	aplay -D hw:1 xxx
> But, 2nd sound card can't probe because of above patch now.
> (component->card indicates 1st card)
> It can be probeed if I used DPCM card (= 1 CPU + 2 Codec), but...
> But, is my understanding wrong ?

ASoC always had the restriction that you can only bind a component to a
single card. Otherwise the internal data structures will get corrupted,
which may result in undefined behavior at a later point. The patch made this
restriction explicit to make sure that issue is caught when it happens and
you don't have dig through crashes from random memory corruption.

Changing this is unfortunately not really trivial.

- Lars